Preheat oven to 350°F. Grease two 9-inch round pans and line with parchment. Whisk flour, sugar, cocoa, baking soda, baking powder, and salt. Combine buttermilk, oil, eggs, and vanilla; stir into dry ingredients. Mix in hot coffee until smooth.

Divide batter between pans. Bake 30-35 minutes until a toothpick comes out with a few moist crumbs. Cool in pans 10 minutes, then turn out to cool completely.

Spread pecans and coconut on a baking sheet. Toast at 350°F for 5-7 minutes until golden and fragrant; let cool.

In a saucepan, whisk evaporated milk, sugar, egg yolks, and butter. Cook over medium heat, stirring constantly, 8-12 minutes until thickened. Remove from heat; stir in vanilla, coconut, and pecans. Cool to room temperature until spreadable.

Level cake layers if needed. Place one layer on a plate; spread half the filling on top. Add second layer; spread remaining filling on top, leaving sides bare.

Slice and serve at room temperature. Refrigerate 20 minutes for cleaner cuts if you like.